I have only high speed on my ac/heat switch. have replace acdelco blower motor resistor 2 times already. works for a while and quits. whatelse do I need to check etc?.

94 CHEVY Silverado ????,heat/ac fan not blowing. K1500?????? Hear clicking when selecting l'm, SET high but not blowing! WITH AIR OR NO A/C? FIRST IS FUSES, MAKE SURE THE BLOWER FUSE IS NOT BLOWN.
EASY NO? CHECK ALL FUSES FIRST. ON ALL ELECTRICS FAILING OF ANY KIND.
BAD FUSE, BAD WIRINIG , BAD CONNECTIONS. OR EVEN BAD RELAYS TO THE BLOWER OR BAD SWITCH BLOW.
THE OLD CARS , HAD A SPEED BLOW , RESISTOR BLOCK
THAT FAILS ON ALL SPEEDS BUT HIGH, SO ITS NOT THAT.
OWN A VOLT METER????
HERE IT IS, ANY OF THIS CAN FAIL THIS OLD
WE USES A VOLTMETER TO FIND THE POINT OF FAILURE.
A SHORTED BLOWER MOTOR CAN BLOW LEFT SIDE TOP
FUSABLE LINK.RIGHT FUSE BLOWN MAKES THE CONTROLLER DEAD.

Could be a number of thing's ! Testing the electrical circuit is the way to find out what's wrong . Using a wiring diagram and a DVOM - digital volt ohm meter . Videos on youtube showing how to test it ! Without testing i would only be guessing . Does it work in high speed ? In high speed it by-passes the resistor . If it doesn't work in any speed more then likely the blower motor is the problem !
Air Speed
The HVAC control assembly applies ground to the blower motor control circuit that corresponds to the selected blower speed. The resistors and the blower motor are in a series circuit. The following list represents the number of resistors in series with the blower motor per particular speed request:
• Low speed--3 resistors
• Medium 1 speed--2 resistors
• Medium 2 speed--1 resistor
When the operator requests High speed, the HVAC control assembly applies ground directly to the blower motor through the high blower motor control circuit. The resistor card has a fusible link which, if blown, will require that the card be replaced.

Blower Motor and Resistor Diagnostics by Wells

a resistor went bad for your blower motor.It is located by the blower motor on a circuit board.You can get the replacement resistor at Radio Shack and solder it in.This fixed my problem

In the beginning you should check for voltage and ground.
The 50amp fuse marked AC powers the blower motor and the motor is grounded.
The high speed relay bypasses the resistor. So you should have power coming from the fuse and thru the high relay. Then the resistor for the other speeds gets power from the heat and ac control module which also controls the blend doors.
You may need a shop manual or repair book to get the diagrams.

you probably need new control switch.

That's what it sounds like to me.

If the blower is making noise than the only thing you can do is replace it.

Blower resistors typically operate by dropping voltage through a set of resistors. The lower the speed the more resistance is needed. High speed requires no resistance and usually bypasses the resistor assembly.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

probley one of five possiabes problems

1. blower motor is bad (if case alot times will take resistor or relay out with it)

2. blower resistor (conrols fan speeds usally one speed will go out first example still have high speed but now low)

3. relay (may be one or up to three) (if more than one usally wont have the resistor stated above)

4. fuses

5. blower switch

do you have feed to blower motor ?? sorry CSI is coming on TV now and er indoors is screaming that i spent too long on here '¡'¡'¡'¡'¡ usual ----typical woman ,if you have her i will throw my jag in the deal for free

this is because your blower motor resisters are burned out for speeds 1,2 & 3. High speed does not have a resister.

Replace the resister. If it goes a 2nd time, it is because your blower motor is failing & drawing too much current.

it is behind the glove box I think. It is in the plenum case where air blowing on it keeps it cool.

Easy repair. May need to access throught glove box which should open all the way down when you squeeze the sides in.

Go to tascafordparts.com for a discounted resister.
Please rate as solved problem if this is what you needed.

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Manual Climate Control System Outputs
Blower Motor Switch Resistor
Blower Motor Resistor Coils Blower Motor Thermal Limiter The heater blower motor switch resistor has the following features:

• The assembly is located on the passenger side of the plenum assembly behind the glove compartment (06010).
• Three resistance elements are mounted on the resistor board to provide four A/C blower motor speeds.
• Depending on the heater blower motor switch position, series resistance is added or bypassed in the A/C blower motor circuit to decrease or increase A/C blower motor speed.
• An overheating protective device (thermal limiter) will open the resistor coil circuit when the temperature reaches 121°C (250°F), interrupting the blower motor operation in all speeds except HI.
• The thermal limiter cannot be reset and is not serviceable.

heres the electrical diag.....